#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
typedef vector<int> vi;
typedef vector<vi> vii;
typedef pair<int,int> pi;
typedef vector<pi> pii;
typedef tuple<int,int,int> ti;
typedef vector<ll> li;
typedef vector<li> lii;
#define REP(i,a,b) for(int i=a;i<b;i++)
#define F first
#define S second
#define PB push_back
#define LSOne(s) ((s)&(-s))
ll INF=1000000000000000010;
int inf=1e9+10;
ll M=1e9+7;
int main() {
// ios::sync_with_stdio(0);
// cin.tie(0);
int n;ll A,B;cin>>n>>A>>B;
ll k=A*B;
vector<pair<ll,ll>> a;
bool flag=0;
REP(i,0,n){
ll x,y;cin>>x>>y;
if(y%k==0&&x%k==0){
a.PB({1,k-1});
flag=1;
}
if(y%k==0){
a.PB({x%k,k-1});
flag=1;
}
else if(x%k==0){
a.PB({1,y%k});
flag=1;
}
else a.PB({x%k,y%k});
}
sort(a.begin(),a.end());
ll ans=a[0].S-a[0].F+1,l=a[0].S;
if(flag)ans++;
int pos=1;REP(i,0,n)
while(pos<n){
while(pos<n&&a[pos].S<=l)pos++;
if(pos==n)break;
ans+=a[pos].S-max(l,a[pos].F-1);
l=a[pos].S;
}
cout<<ans;
}
